Catalytic cracking catalyst

ABSTRACT

Catalytic cracking catalysts, the process of their preparation and the process of their use.

This application is a continuation of prior U.S. application Ser. No.500,446, filed June 2, 1983, now abandoned.

FIELD OF THE INVENTION

The present invention relates to cracking catalysts and the process oftheir use. The cracking catalysts are derived from novel zeoliticaluminosilicates set forth in copending U.S. Ser. No. 315,853, filedOct. 28, 1981 now U.S. Pat. No. 4,503,023.

BACKGROUND OF THE INVENTION

The prior art dealing with catalytic cracking catalysts is voluminouswith a basic goal being the preparation of modified zeolites for use ascracking catalysts. The prior art tends to deal with various ways inwhich the activity and stability of the catalyst may be improved.

It has been disclosed that the steam and thermal stability of zeolitescan be improved by the use of zeolites having a low level of alkalimetal content and a unit cell size less than about 24.45 Angstroms (See:U.S. Pat. Nos. 3,293,192 and Re. 28,629 (Reissue of U.S. Pat. No.3,402,996)).

Further, it has been disclosed (U.S. Pat. No. 3,591,488) that thehydrogen or ammonium form of a zeolite may be treated with H₂ O at atemperature ranging from about 800° to about 1500° F., and thensubsequently cation exchange the steam and water treated zeolite withcations which may be rare earth metal cations. The method increases thesilica to alumina mole ratio of the zeolite and also the defectstructure.

Another approach taken in an attempt to improve catalytic activity forfaujasite-type zeolites is disclosed in U.S. Pat. No. 4,224,188 wherethe patentee discloses that improved catalytic activity offaujasite-type zeolites can be obtained if the zeolite is first aluminumexchanged and then ammonium exchanged. It is interesting to note that ifthe ammonium exchange was carried out before the aluminum exchange thatno improvement in activity or thermal stability was observed. This isconsistent with the publication of K. M. Wang et al. at J. Catal. 24,262 (1972) which teaches that the hydrogen form of zeolite Y is unstableto hydrothermal treatment when such are aluminum exchanged.

U.S. Pat. No. 4,219,466 purports to disclose that ion-exchange(ammonium, aluminum and rare earth cations) of a silica-alumina hydrogelwhich contains a zeolite gives a catalyst with improved characteristics.The examples with respect to aluminum exchanged materials show that thealuminum exchange exhibited no improvement as a catalyst.

In copending U.S. Ser. No. 657,417 filed Oct. 3, 1984, there isdisclosed improved cracking catalysts derived from Zeolite LZ-210, asdisclosed in U.S. Pat. No. 4,503,023 which issued on Mar. 5, 1985. Theinstant invention relates to Group IIIA ion-exchanged LZ-210 basedcatalysts.

SUMMARY OF THE INVENTION

The process for the catalytic cracking of a crude oil feedstock toproduce lower boiling hydrocarbons which comprises contacting saidfeedstock with a zeolitic aluminosilicate which has a mole ratio ofoxide in the dehydrated state of

    (0.85-1.1)M.sub.2/n O:Al.sub.2 O.sub.3 :xSiO.sub.2

wherein M is a cation having a valence of "n"; x has a value greaterthan 6.0; having a X-ray powder diffraction pattern having at least thed-spacings of Table A; having extraneous silicon atoms in the crystallattice in the form of framework SiO₄ tetrahedra, wherein saidaluminosilicate has been ion-exchanged with Group IIIA cations. Inaddition, the Group IIIA exchanged LZ-210 may be heated for an effectivetemperature and for effective time in the presence of an effectiveamount of steam, and/or may be ion-exchanged with a multivalent cationother than Group IIIA, e.g. rare earth, to provide catalystcompositions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to new catalytic cracking catalysts, theirmethod of preparation and to the process of their use in catalyticcracking processes.

The catalytic cracking catalysts of the instant invention are derivedfrom a novel class of zeolitic aluminosilicates denominated LZ-210 incopending U.S. Ser. No. 315,853, filed Oct. 28, 1981, said applicationbeing incorporated herein by reference thereto.

It has been discovered that LZ-210 may be ion-exchanged with Group IIIAcations to give zeolites which when employed in catalytic crackingcatalysts have improved catalytic stability and, accordingly, arebelieved to have long catalyst life when employed in cracking catalystformulations.

The catalysts of the present invention will be referred to herein,solely for the purpose of reference herein, as LZ-210-A to denominate anLZ-210 composition ion-exchanged with a Group IIIA cation-containingsolution. Other components and processing steps may be provided withLZ-210-A to provide the final catalytic cracking catalyst and exemplaryof such other components and/or processing steps will be discussedhereinafter.

LZ-210-A compositions are prepared using LZ-210 as described in U.S.Ser. No. 315,853, above mentioned with a general description of LZ-210being as follows:

LZ-210

Aluminosilicates having in the dehydrated state, a chemical compositionexpressed in terms of mole ratios of oxides as

    (0.85-1.1)M.sub.2/n O:Al.sub.2 O.sub.3 :xSiO.sub.2

wherein "M" is a cation having the valence "n"; and "x" has a valuegreater than 6, preferably greater than 7.0; having an X-ray powderdiffraction pattern having at least the d-spacings set forth in Table A,below; and having extraneous silicon atoms in its crystal lattice in theform of SiO₄ tetrahedra, preferably in an average amount of at least 1.0per 10,000A³.

For purposes of reference herein the framework composition are bestexpressed in terms of mole fractions of framework tetrahedra TO₂. Thestarting zeolite may be expressed as:

    (Al.sub.a Si.sub.b □).sub.z O.sub.2

whereas "a" is the mole fraction of aluminum tetrahedra in theframework; "b" is the mole fraction of silicon tetrahedra in theframework; □ denotes defect sites and "z" is the mole fraction of defectsites in the zeolite framework. In many cases the "z" value for thestarting zeolite is zero and the defect sites are simply eliminated fromthe expression. Numerically the sum of the values a+b+z=1.

The zeolite product of the fluorosilicate treatment, expressed in termsof mole fraction of framework tetrahedra (TO₂) will have the form

    [Al.sub.(a-N) Si.sub.b+(N-Δz) □.sub.z ]O.sub.2

wherein: "N" is defined as the mole fraction of aluminum tetrahedraremoved from the framework during the treatment; "a" is the molefraction of aluminum tetrahedra present in the framework of the startingzeolite; "b" is the mole fraction of silicon tetrahedra present in theframework of the starting zeolite; "z" is the mole fraction of defectsites in the framework; (N-Δz) is the mole fraction increase in silicontetrahedra resulting from the fluoro-silicate treatment; "Δz" is the netchange in the mole fraction of defect sites in the zeolite frameworkresulting from the treatment Δz=z (product zeolite)-z (starting zeolite)The term "Defect Structure Factor" for any given zeolite is equivalentto the "z" value of the zeolite. The net change in Defect StructureFactors between the starting zeolite and the product zeolite isequivalent to "Δz". Numerically, the sum of the values is representedby:

    (a-N)+[b+(N-Δz)×z=1

A subclass of the above LZ-210 compositions, i.e. those which arecharacterized by having both high molar SiO₂ /Al₂ O₃ ratios and lowDefect Structure Factors (as hereinafter discussed), can be defined ashaving a chemical composition expressed in terms of mole fractions offramework tetrahedra as:

    [Al.sub.(a-N) Si.sub.b+(N-Δz) □z-]O.sub.2

wherein:the mole fraction of aluminum removed from the framework of thestarting zeolite is "N"; ##EQU1## has a value greater than 6, preferablygreater than 7.0; the change in defect structure factor Δz is less than0.08 and preferably less than 0.05; an increased silicon content in theframework, ##EQU2## of at least 0.5; and a cation equivalentexpressed asa monovalent cation species, M⁺ /Al, from 0.85 to 1.1 and thecharacteristic crystal structure of zeolite Y as indicated by an X-raypowder diffraction pattern having at least the d-spacings set forthbroadly in Table A.

                  TABLE A                                                         ______________________________________                                        d(A)                 Intensity                                                ______________________________________                                         14.3-13.97          very strong                                              8.71-8.55            medium                                                   7.43-7.30            medium                                                   5.66-5.55            strong                                                   4.75-4.66            medium                                                   4.36-4.28            medium                                                   3.75-3.69            strong                                                   3.30-3.23            strong                                                   2.85-2.79            strong                                                   ______________________________________                                    

Zeolite LZ-210 as defined above will have cubic unit cell dimension,a_(o), of less than 24.61 Angstroms, an adsorption capacity for watervapor at 25° C. and 4.6 Torr water vapor pressure of at least 20 weightpercent based on the anhydrous weight of the zeolite, and preferably anoxygen adsorption capacity at 100 Torr and -183° C. of at least 25weight percent.

LZ-210 can be prepared by a method which removes framework aluminum froma zeolite having SiO₂ /Al₂ O₃ molar ratios of about 3 or greater andsubstituting therefor silicon from a source extraneous to the startingzeolite. By such a procedure it is possible to create more highlysiliceous zeolite species which have the same crystal structure as wouldresult by direct synthesis if such synthesis method were known. Theprocess disclosed in copending U.S. Ser. No. 315,853 comprisescontacting a crystalline zeolite having pore diameters of at least about3 Angstroms and having a molar SiO₂ /Al₂ O₃ ratio of at least 3, with afluorosilicate salt, preferably in an amount of at least 0.0075 molesper 100 grams of zeolite starting material, said fluorosilicate saltbeing in the form of an aqueous solution having a pH value in the rangeof 3 to about 7, preferably 5 to about 7, and brought into contact withthe zeolite either incrementally or continuously at a slow rate wherebyframework aluminum atoms of the zeolite are removed and replaced byextraneous silicon atoms from the added fluorosilicate.

LZ-210 can be prepared from a conventionally prepared zeolite Y whichhas a molar SiO₂ /Al₂ O₃ ratio of less than 6 by using the above processto increase the SiO₂ /Al₂ O₃ ratio greater than 6. A preferred procedurecomprises:

(a) providing a zeolite Y composition having a molar SiO₂ /Al₂ O₃ ratioless than that of the final product and preferably less than 6.0;

(b) contacting and reacting at a temperature of from 20° to 95° C., saidzeolite Y with a fluorosilicate, preferably ammonium fluorosilicate; thefluorosilicate solution, being in the form of an aqueous solution at apH in the range of 5 to about 7, is brought into contact with thezeolite either incrementally or continuously at a slow rate such that asufficient proportion of the framework aluminum atoms removed arereplaced by silicon atoms to retain at least 80 percent, preferably atleast 90 percent, of the crystal structure of the starting zeolite Y;and

(c) isolating the zeolite having an enhanced framework silicon contentfrom the reaction mixture.

The starting zeolite Y composition can be synthesized by any of theprocesses well known in the art. A representative process is disclosedin U.S. Pat. No. 3,130,007.

For reasons more fully explained hereinafter, it is necessary that thestarting zeolite be able to withstand the initial loss of frameworkaluminum atoms to at least a modest degree without collapse of thecrystal structure unless the process is to be carried out at a very slowpace. Accordingly it is preferred that the value for "x" in the formulaabove be at least about 3.0. Also it is preferred that at least about50, and more preferably at least 95%, of the AlO₄ tetrahedra of thenaturally occurring or as-synthesized zeolite are present in thestarting zeolite. Most advantageously the starting zeolite contains asmany as possible of its original AlO₄ tetrahedra, i.e. has not beensubjected to any post-formation treatment which either extensivelyremoves aluminum atoms from their original framework sites or convertsthem from the normal conditions of 4-fold coordination with oxygen.

The cation population of the starting zeolite is not a critical factorinsofar as substitution of silicon for framework aluminum is concerned,but since the substitution mechanism involves the in situ formation ofsalts of at least some of the zeolitic cations, it is advantageous thatthese salts be water-soluble to a substantial degree to facilitate theirremoval from the silica-enriched zeolite product. It is found thatammonium cations for the most soluble salt in this regard and it isaccordingly preferred that at least 50 percent, most preferably 85 ormore percent, of the zeolite cations be ammonium cations. Sodium andpotassium, two of the most common original cations in zeolites are foundto form Na₃ AlF₆ and K₃ AlF₆ respectively, both of which are only verysparingly soluble in either hot or cold water. When these compounds areformed as precipitates within the structural cavities of the zeolitethey are quite difficult to remove by water washing. Their removal,moreover, is important if thermal stability of the zeolite product isdesired since the substantial amounts of fluoride can cause crystalcollapse at temperatures as low as 500° C.

The fluorosilicate salt used as the aluminum extractant and also as thesource of extraneous silicon which is inserted into the zeolitestructure in place of the extracted aluminum can be any of thefluorosilicate salts having the general formula

    (A).sub.2/b SiF.sub.6

wherein A is preferably a metallic or non-metallic cation other than H⁺having the valence "b". Cations represented by "A" are alkylammonium,NH₄ ⁺, Mg⁺⁺, Li⁺, Na⁺, K⁺, Ba⁺⁺, Cd⁺⁺, Cu⁺, H⁺, Cu⁺⁺, Ca⁺⁺, Cs⁺, Fe⁺⁺,Co⁺⁺, Pb⁺⁺, Mn⁺⁺, Rb⁺, Ag⁺, Sr⁺⁺, Tl⁺, and Zn⁺⁺. The ammonium cationform of the fluorosilicate is highly preferred because of itssubstantial solubility in water and also because the ammonium cationsform water soluble by-product salts upon reaction with the zeolite,namely (NH₄)₃ AlF₆.

In certain respects, the manner in which the fluorosilicate and startingzeolite are brought into contact and the overall process of substitutingsilicon for aluminum in the zeolite framework is a two step process inwhich the aluminum extraction step will, unless controlled, proceed veryrapidly while the silicon insertion is relatively very slow. Ifdealumination becomes too extensive without silicon substitution, thecrystal structure becomes seriously degraded and ultimately collapses.While we do not wish to be bound by any particular theory, it appearsthat the fluoride ion is the agent for the extraction of frameworkaluminum in accordance with the equation ##STR1## It is, therefore,essential that the initial dealumination step be inhibited and thesilicon insertion step be promoted to achieve the desired zeoliteproduct. It is found that the various zeolite species have varyingdegrees of resistance toward degradation as a consequence of frameworkaluminum extraction without silicon substitution. In general the rate ofaluminum extraction is decreased as the pH of the fluorosilicatesolution in contact with the zeolite is increased within the range of 3to 7, and as the concentration of the fluorosilicate in the reactionsystem is decreased. Also increasing the reaction temperature tends toincrease the rate of silicon substitution. Whether it is necessary ordesirable to buffer the reaction system or strictly limit thefluorosilicate concentration is readily determined for each zeolitespecies by routine observation.

Theoretically, there is no lower limit for the concentration offluorosilicate salt in the aqueous solution employed, provided of coursethe pH of the solution is high enough to avoid undue destructive acidicattack on the zeolite structure apart from the intended reaction withthe fluorosilicate. Very slow rates of addition of fluorosilicate saltsinsure that adequate time is permitted for the insertion of silicon as aframework substitute for extracted aluminum before excessive aluminumextraction occurs with consequent collapse of the crystal structure.Practical commercial considerations, however, require that the reactionproceed as rapidly as possible, and accordingly the conditions ofreaction temperature and reagent concentrations should be optimized withrespect to each zeolite starting material. In general the more highlysiliceous the zeolite, the higher the permissible reaction temperatureand the lower the suitable pH conditions. In general the preferredreaction temperature is within the range of 50° to 95° C., buttemperatures as high as 125° C. and as low as 20° C. have been suitablyemployed in some instances. At pH values below about 3 crystaldegradation is generally found to be unduly severe, whereas at pH valueshigher than 7, silicon insertion is unduly slow. The maximumconcentration of fluorosilicate salt in the aqueous solution employedis, of course, interdependent with the temperature and pH factors andalso with the time of contact between the zeolite and the solution andthe relative proportions of zeolite and fluorosilicate. Accordingly itis possible that solutions having fluorosilicate concentrations of fromabout 10₋₃ moles per liter of solution up to saturation can be employed,but it is preferred that concentrations in the range of 0.5 to 1.0 molesper liter of solution be used. These concentration values are withrespect to true solutions, and are not intended to apply to the totalfluorosilicate in slurries of salts in water. As illustratedhereinafter, even very slightly soluble fluorosilicates can be slurriedin water and used as a reagent--the undissolved solids being readilyavailable to replace dissolved molecular species consumed in reactionwith the zeolite. As stated hereinabove, the amount of dissolvedfluorosilicates employed with respect to the particular zeolite beingtreated will depend to some extent upon the physical and chemicalproperties of the individual zeolites as well as other specificationsherein contained in this application. However, the minimum value for theamount of fluorosilicate to be added should be at least equivalent tothe minimum mole fraction of aluminum to be removed from the zeolite.

In this disclosure, including the appended claims, in specifyingproportions of zeolite starting material or adsorption properties of thezeolite product, and the like, the anhydrous state of the zeolite willbe intended unless otherwise stated. The anhydrous state is consideredto be that obtained by heating the zeolite in dry air at 100° C. forabout 1 to 2 hours.

It is apparent from the foregoing that, with respect to reactionconditions, it is desirable that the integrity of the zeolite crystalstructure is substantially maintained throughout the process, and thatin addition to having extraneous (non-zeolitic) silicon atoms insertedinto the lattice, the zeolite retains at least 60 and preferably atleast 90 percent of its original crystallinity. A convenient techniquefor assessing the crystallinity of the products relative to thecrystallinity of the starting material is the comparison of the relativeintensities of the d-spacings of their respective X-ray powderdiffraction patterns. The sum of the peak heights, in terms of arbitraryunits above background, of the starting material is used as the standardand is compared with the corresponding peak heights of the products.When, for example, the numerical sum of the peak heights of the productis 85 percent of the value of the sum of the peak heights of thestarting zeolite, then 85 percent of the crystallinity has beenretained. In practice it is common to utilize only a portion of thed-spacing peaks for this purpose, as for example, five of the sixstrongest d-spacings. In zeolite Y these d-spacings correspond to theMiller Indices 331, 440, 533, 642 and 555. Other indicia of thecrystallinity retained by the zeolite product are the degree ofretention of surface area and the degree of retention of the adsorptioncapacity. Surface areas can be determined by the well-knownBrunauer-Emmett-Teller method (B-E-T). J. Am. Chem. Soc. 60 309 (1938)using nitrogen as the adsorbate. In determining the adsorption capacity,the capacity for oxygen at -183° C. at 100 Torr is preferred.

All available evidence, to date, indicates that the above describedprocess is unique in being able to produce zeolites essentially free ofdefect structure yet having molar SiO₂ /Al₂ O₃ ratios higher than thoseheretofore obtained by direct hydrothermal synthesis i.e., no otherprocess is known to date for preparing LZ-210. The products resultingfrom the operation of the process share the common characteristic ofhaving a higher molar SiO₂ /Al₂ O₃ ratio than previously obtained foreach species by direct hydrothermal synthesis by virtue of containingsilicon from an extraneous, i.e. non-zeolitic, source, preferably inconjunction with a crystal structure which is characterized ascontaining a low level of tetrahedral defect sites. This defectstructure, if present, is revealed by the infrared spectrum of zeolitesin the hydroxyl-stretching region.

In untreated, i.e. naturally occurring or as-synthesized zeolites theoriginal tetrahedral structure is conventionally represented as ##STR2##After treatment with a complexing agent such asethylene-diaminetetraacetic acid (H₄ EDTA) in which a stoichiometricreaction occurs whereby framework aluminum atoms along with anassociated cation such as sodium is removed as NaAlEDTA, it ispostulated that the tetrahedral aluminum is replaced by four protonswhich form a hydroxyl "nest", as follows: ##STR3## The infrared spectrumof the aluminum depleted zeolite will show a broad nondescriptadsorption band beginning at about 3750 cm⁻¹ and extending to about 3000cm⁻¹. The size of this absorption band or envelope increases withincreasing aluminum depletion of the zeolite. The reason that theabsorption band is so broad and without any specific absorptionfrequency is that the hydroxyl groups in the vacant sites in theframework are coordinated in such a way that they interact with eachother (hydrogen bonding). The hydroxyl groups of adsorbed watermolecules are also hydrogen-bonded and produce a similar broadabsorption band as do the "nest" hydroxyls. Also, certain other zeolitichydroxyl groups, exhibiting specific characteristic absorptionfrequencies within the range of interest, will if present, causeinfrared absorption bands in these regions which are superimposed on theband attributable to the "nest" hydroxyl groups. These specifichydroxyls are created by the decomposition of ammonium cations ororganic cations present in the zeolite.

It is, however, possible to treat zeolites, prior to subjecting them toinfrared analysis, to avoid the presence of the interferring hydroxylgroups and thus be able to observe the absorption attributable to the"nest" hydroxyls only. The hydroxyls belonging to adsorbed water wereavoided by subjecting the hydrated zeolite sample to vacuum activationat a moderate temperature of about 200° C. for about 1 hour. Thistreatment permits desorption an removal of the adsorbed water. Completeremoval of adsorbed water can be ascertained by noting when the infraredabsorption band at about 1640 cm⁻¹, the bending frequency of watermolecules, has been removed from the spectrum.

The decomposable ammonium cations can be removed, at least in largepart, by ion-exchange and replaced with metal cations, preferably bysubjecting the ammonium form of the zeolite to a mild ion exchangetreatment with an aqueous NaCl solution. The OH absorption bandsproduced by the thermal decomposition of ammonium cations are therebyavoided. Accordingly the absorption band over the range of 3745 cm⁻¹ toabout 3000 cm⁻¹ for a zeolite so treated is almost entirely attributableto hydroxyl groups associated with defect structure and the absoluteabsorbance of this band can be a measure of the degree of aluminumdepletion.

It is found, however, that the ion-exchange treatment, which mustnecessarily be exhaustive even though mild, required considerable time.Also the combination of the ion-exchange and the vacuum calcination toremove adsorbed water does not remove every possible hydroxyl other thandefect hydroxyls which can exhibit absorption in the 3745 cm⁻¹ to 3000cm⁻¹ range. For instance, a rather sharp band at 3745 cm⁻¹ has beenattributed to the Si-OH groups situated in the terminal latticepositions of the zeolite crystals and to amorphous (non-zeolitic) silicafrom which physically adsorbed water has been removed. For these reasonswe prefer to use a somewhat different criterion to measure the degree ofdefect structure in the zeolite products of this invention.

In the absence of hydrogen-bonded hydroxyl groups contributed byphysically adsorbed water, the absorption frequency least affected byabsorption due to hydroxyl groups other than those associated withframework vacancies or defect sites is at 3710±5 cm⁻¹. Thus the relativenumber of defect sites remaining in a zeolite product of this inventioncan be gauged by first removing any adsorbed water from the zeolite,determining the value of the absolute absorbance in its infraredspectrum at a frequency of 3710 cm⁻¹, and comparing that value with thecorresponding value obtained from the spectrum of a zeolite having aknown quantity of defect structure. The following specific procedure hasbeen arbitrarily selected and used to measure the amount of defectstructure in the products prepared in the Examples appearinghereinafter. Using the data obtained from this procedure it is possible,using simple mathematical calculation, to obtain a single andreproducible value hereinafter referred to as the "Defect StructureFactor", denoted hereinafter by the symbol "z", which can be used incomparing and distinguishing the present novel zeolite compositions fromtheir less-siliceous prior known counter-parts and also with equallysiliceous prior known counter-parts prepared by other techniques.

DEFECT STRUCTURE FACTOR

(A) Defect Structure Zeolite Standard.

Standards with known amounts of defect structure can be prepared bytreating a crystalline zeolite of the same species as the product samplewith ethylenediaminetetraacetic acid by the standard procedure of Kerras described in U.S. Pat. No. 3,442,795. In order to prepare thestandard it is important that the starting zeolite be well crystallized,substantially pure and free from defect structure. The first two ofthese properties are readily determined by conventional X-ray analysisand the third by infrared analysis using the procedure set forth in part(B) hereof. The product of the aluminum extraction should also be wellcrystallized and substantially free from impurities. The amount ofaluminum depletion, i.e., the mole fraction of tetrahedral defectstructure of the standard samples can be ascertained by conventionalchemical analytical procedure. The molar SiO₂ /Al₂ O₃ ratio of thestarting zeolite used to prepare the standard sample in any given caseis not narrowly critical, but is preferably within about 10% of themolar SiO₂ /Al₂ O₃ ratio of the same zeolite species used as thestarting material in the practice of the process of the presentinvention.

(B) Infrared Spectrum of Product Samples and Defect Structure ZeoliteStandard.

Fifteen milligrams of the hydrated zeolite to be analyzed are pressedinto a 13 mm. diameter self-supporting wafer in a KBr die under 5000lbs. pressure. The wafer is then heated at 200° C. for 1 hour at apressure of not greater than 1×10⁻⁴ mm. Hg to remove all observabletraces of physically adsorbed water from the zeolite. This condition ofthe zeolite is evidenced by the total absence of an infrared adsorptionband at 1640 cm⁻¹. Thereafter, and without contact with adsorbablesubstances, particularly water vapor, the infrared spectrum of the waferis obtained on an interferometer system at 4 cm⁻¹ resolution over thefrequency range of 3745 to 3000 cm⁻¹. Both the product sample and thestandard sample are analyzed using the same interferometer system toavoid discrepancies in the analysis due to different apparatus. Thespectrum, normally obtained in the transmission mode of operation ismathematically converted to and plotted as wave number vs. absorbance.

(C) Determination of the Defect Structure Factor.

The defect structure factor (z) is calculated by substituting theappropriate data into the following formula: ##EQU3## whereinAA.sub.(ps) is the infrared absolute absorbance measured above theestimated background of the product sample at 3710 cm⁻¹ ; AA.sub.(std)is the absolute absorbance measured above the background of the standardat 3710 cm⁻¹ and the mole fraction of defects in the standard aredetermined in accordance with part (A) above.

Once the defect structure factor, z, is known, it is possible todetermine from wet chemical analysis of the product sample for SiO₂, Al₂O₃ and the cation content as M_(2/n) /O whether silicon has beensubstituted for aluminum in the zeolite as a result of the treatment andalso the efficiency of any such silicon substitution.

The fact that the present process results in zeolite products havingsilicon substituted for aluminum in the framework is substantiated bythe framework infrared spectrum in addition to the hydroxyl regioninfrared spectrum. In the former, there is a shift to higher wavenumbers of the indicative peaks and some sharpening thereof in the caseof the present products, as compared to the starting zeolite, which isdue to an increased SiO₂ /Al₂ O₃ molar ratio.

The essential X-ray powder diffraction patterns appearing in thisspecification and referred to in the appended claims are obtained usingstandard X-ray powder diffraction techniques. The radiation source is ahigh-intensity, copper target, x-ray tube operated at 50 Kv and 40 ma.The diffraction pattern from the coproper K alpha radiation and graphitemonochromator is suitably recorded by an X-ray spectrometerscintillation counter, pulse-height analyzer and strip-chart recorder.Flat compressed powder samples are scanned at 2° (2 theta) per minute,using a 2 second time constant. Interplanar spacings (d) are obtainedfrom the position of the diffraction peaks expressed as 2 theta, where 2theta is the Bragg angle as observed on the strip chart. Intensities aredetermined from the heights of diffraction peaks after subtractingbackground.

In determining the cation equivalency, i.e. the molar ratio M_(2/n)O/Al₂ O₃ in each zeolite product, it is advantageous to perform theroutine chemical analysis on a form of the zeolite in which "M" is amonovalent cation other than hydrogen. This avoids the uncertainty whichcan arise in the case of divalent or polyvalent metal zeolite cations asto whether the full valence of the cation is employed in balancing thenet negative charge associated with each AlO₄ -tetrahedron or whethersome of the positive valence of the cation is used in bonding with OH⁻or H₃ O⁺ ions.

The preferred novel crystalline aluminosilicate compositions of thepresent invention will contain a chemical or molar framework compositionwhich can be determined from the expression of mole fractions offramework tetrahedra previously described:

    [Al.sub.(a-N) Si.sub.b+(N-Δz) □.sub.z ]O.sub.2

wherein: the framework Si/Al ratio is determined by ##EQU4## and isnumerically greater than 3; the mole fraction of silicon tetrahedrasubstituted into the framework of the product zeolite (N-Δz) isincreased by at least a value for ##EQU5## which is numerically 0.5, thechange in Defect Structure Factor Δz is increased by less than 0.08 andpreferably less than 0.05.

Moreover, regardless of the Defect Structure Factor of any zeolitematerial which has been treated according to the present process, it isnovel by virtue of having had extraneous silicon inserted into itscrystal lattice and having a molar SiO₂ /Al₂ O₃ ratio greater thanheretofore obtained by direct hydrothermal synthesis. This isnecessarily the case since all other methods for increasing the SiO₂/Al₂ O₃ ratio of a zeolite crystal must remove framework aluminum atoms,and unless at least one of those removed aluminum atoms is replaced by asilicon atom from a source other than the crystal itself, the absolutedefect structure content of the crystal must be greater than that ofLZ-210.

ZEOLITE LZ-210-A

The catalysts of the instant invention are prepared by use of a zeoliteprepared by the treatment of LZ-210 having a SiO₂ to Al₂ O₃ ratio ofgreater than 6.0 and preferably, greater than 7.0 with Group IIIAcations.

LZ-210-A can be prepared by treating an LZ-210 material with aneffective amount of at least one Group IIIA cation by treatment with asolution of a Group IIIA salt under effective ion-exchange conditions.The term "Group IIIA cation" is meant to denominate hydroxylatedcations, complexed cations, solvated cations and the like. Sucheffective conditions will result in an average of at least one GroupIIIA cation being provided to the LZ-210 material per every unit cell,preferably at least 2 per every unit cell and most preferably at least 3per unit cell. Although the Group IIIA cation exchange conditions arenot critical, typical exchange conditions would be to exchange theLZ-210 in an aqueous slurry of a water soluble Group IIIA salt at atemperature between about 20° C. and about 120° C. for a period greaterthan about 0.25 hour at atmospheric pressure. The Group IIIA salt can bemost any salt which contains Group IIIA cations in solution, preferablyaqueous solution, and it may be nitrates, chlorides, organic salts andthe like. Preferably the salt is an aluminum salt. Although water is thepreferred solvent for the Group IIIA salt it is within the scope of thisinvention to employ organic solvents, inorganic solvents, and mixturesof organic and inorganic solvents.

In addition to the Group IIIA cation exchange the LZ-210 material may besubject to further treatments including thermal treatment andion-exchange with ammonium and/or multivalent cations other than GroupIIIA cations.

The term "thermal treatment" is employed here to denominate both athermal calcination and a hydrothermal calcination, i.e., calcination inthe presence of steam. The thermal treatment is carried out at aneffective temperature and time and when a hydrothermal treatment in thepresence of an effective amount of steam, to provide an LZ-210-A basedcatalyst. The thermal treatment is typically carried out at atemperature in excess of 500° C. for a period in excess of 0.25 hoursand when the thermal treatment is a hydrothermal treatment it istypically carried out in the presence of at least about 20 percent byvolume steam. The source of the steam is not important and may beprovided from an external source or may be generated in situ at thetemperatures employed for the hydrothermal treatment.

LZ-210-A may also be subjected to ion-exchange or impregnation withammonium and/or a multivalent cations other than Group IIIA cations bycontacting LZ-210 or LZ-210-A with a solution containing ammonium and/orat least one multi-valent cation selected from the group consisting ofcations of Group IIA and rare earth cations selected from the groupconsisting of lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, yttribium, lutetium and mixtures thereof. As a result ofion-exchange of the LZ-210 or LZ-210-A, at least one cation ision-exchanged with the cations initially present. The cation(s) istypically present in an amount that removes at least about 2 ionexchange percent of the cations (other than cations of Group IIIA)present in the starting LZ-210-A material and is preferably present inan amount greater than about 5.0 ion exchange percent and morepreferably between about 16 ion exchange percent and about 80 ionexchange percent.

Catalysts are prepared using LZ-210-A derived from LZ-210 materialshaving a silica to alumina ratio of greater than 6, preferably greaterthan 7. As above noted, the preparation of LZ-210-A can involve severaloptional steps other than the Group IIIA cation exchange, includingmultivalent cation exchange (other than Group IIIA) and/or thermaltreatment. The various processing steps employed in conjunction withLZ-210-A which may be employed to prepare a given catalyst (containingLZ-210-A) are denominated herein by a shorthand notation where thefollowing notations have the following general meanings:

(i) LZ-210 has been exchanged with aluminum cations;

(ii) LZ-210 has been exchanged with a multivalent cation other thanGroup IIIA;

(iii) thermal treatment; and

(iv) LZ-210 has been ion exchanged with ammonium cations.

The above steps can be employed in a sequential manner to set forth theprocessing sequences employed for a given catalyst and may be employedin any order for one or more times.

The Group IIIA ion exchange step, (i), can be carried out either beforeor after steps (ii), (iii), or (iv) but is in most cases carried outafter any step (iv). The various ion-exchanges (Group IIIA, ammoniumand/or the multivalent cation exchange) are generally carried out bypreparing a slurry of the zeolite by adding about 5 to 15 volumes ofwater per volume of zeolite, after which a solution is added. The ionexchange is generally carried out at room temperature (18° C. to 22° C).The resulting solution may then heated to above about 50° C. and stirredat this temperature for about 0.5 to 3 hours. This mixture is thenfiltered and water washed to remove excess anion present as a result ofthe solution containing the cation.

The ammonium ion exchange step is preferably carried out by slurryingthe zeolite with between 5 to 15 volumes of the ammonium-containingsolution per volume of catalyst after which an ammonium salt is added tothe slurry. The resulting mixture is typically heated to a temperatureabove about 50° C. for a period between about 0.5 to 3 hours. Themixture is filtered and water washed until excess anion from theammonium salt is removed. The ammonium ion exchange process is typicallyrepeated one or more times according to the above described procedure.

Catalyst LZ-210-A is typically employed with inorganic oxide matrix inan amount between about 1 percent and about 99 percent by weight andpreferably between about 1 percent and about 90 percent by weight basedon the total weight of matrix and zeolite. When a matrix is employed itmay be admired with LZ-210 before or after steps (i) to (iv) are carriedout, i.e., the matrix may be admixed with LZ-210 prior to step (i). Thematrix may be inorganic matrices which are typically employed in FCCcatalysts including: amorphous catalytic inorganic oxides, clays,silica, alumina, silica-alumina, silica-zirconia, silica-magnesia,alumina-boria, alumina-titania and the like and mixtures thereof. Thematrix may be in the form of a sol, hydrogel or gel and is typically analumina or amorphous silica-alumina component such as those employed ina formulating conventional silica-alumina cracking catalyst, severaltypes and compositions of which are commercially available. The matrixmay itself provide a catalytic effect or it may be essentially inert.The matrix may act as a "binder" in some instances. The final catalystwill be spray dried or formed without the need of a binder. Thesematerials may be prepared as a cogel of silica and/or alumina or may beprecipitated on a preformed and preaged hydrogel. Silica may be presentas a major component in the solids present in said gels, e.g. present inan amount between about 55 and about 99 weight percent and preferablybetween about 70 and about 90 weight percent. The silica may also beemployed in the form of a cogel comprising about 75 weight percentsilica and about 25 weight percent alumina or comprising about 87 weightpercent silica and about 13 weight percent alumina. The inorganic oxidematrix component will typically be present in the catalyst in an amountbetween about 20 and about 99 weight percent, preferably between about50 and about 90 weight percent, based on the total catalyst. It is alsowithin the scope of the instant invention to employ other materials withthe LZ-210-A in the final cracking catalysts, including various othertypes of molecular sieves, zeolites, clays, carbon monoxide oxidationpromoters, etc.

Mixtures of LZ-210-A, alumina, silica, silica-alumina and/or anotherinorganic matrix are typically formed into a final form for the catalystby standard catalyst forming techniques including spray-drying,pelleting, extrusion and other suitable means. For example, one inchextruded pellets may be dried in air at about 110° C. and then calcined.

Catalytic cracking catalysts of the present invention may be prepared byany one of the above mentioned several methods of extrusion, pelleting,spray-drying and other conventional methods. One method of preparingsuch catalysts employing silica-alumina and porous alumina is to reactsodium silicate with a solution of aluminum sulfate to form asilica/alumina hydrogel slurry which is then aged to give the desiredpore properties, filtered to remove a considerable amount of theextraneous and undesired sodium and sulfate ions and then reslurried inwater. The alumina may be prepared by reacting solutions of sodiumaluminate and aluminum sulfate under suitable conditions, aging theslurry to give the desired pore properties of the alumina, filteringdrying, reslurry in water to remove sodium and sulfate ions and dryingto reduce volatile matter content to less than 15 weight percent. Thealumina may then be slurried in water and blended in proper amounts,with a slurry of silica-alumina hydrogel. The LZ-210-A component maythen be added to this blend. A sufficient amount of each component isutilized to give the desired final composition. The resulting mixture isthen filtered to remove a portion of the remaining extraneous solublesalts therefrom. The filtered mixture is then dried to produce driedsolids. The dried solids are subsequently reslurried in water and washedsubstantially free of the undesired soluble salts. The catalyst is thendried to a residual water content of less than about 15 weight percent.The catalyst is typically recovered after calcination.

Catalytic cracking with the catalyst of the present invention can beconducted in any conventional catalytic cracking manner. Suitablecatalytic cracking conditions include a temperature ranging from about700° F. to about 1300° F. and a pressure ranging from aboutsubatmospheric to several atmospheres, typically from about atmosphericto about 100 psig. The process may be carried out in a fixed bed, movingbed, ebullating bed, slurry, transferline, or fluidized bed operation.The catalyst of the present invention can be used to convert any of theconventional hydrocarbon feeds used in catalytic cracking, that is, itcan be used to crack naphthas, gas oil and residual oils having a highcontent of metal contaminants. It is especially suited for crackinghydrocarbons boiling in the gas oil range, that is, hydrocarbon oilshaving an atmospheric pressure boiling point ranging from about 420° toabout 1100° F. to naphthas to yield not only products having a lowerboiling point than the initial feed but also products having an improvedoctane number.

In addition, catalysts LZ-210-A derived are believed to be useful in anFCC (fluid catalytic cracking) process wherein a carbon-hydrogenfragmentation compound (CHFC) employed in admixture with the crude oilfeed. Such a process will be referred to herein as an FCC-CHFC process.

The term "carbon-hydrogen fragmentation compound(s)" is employed hereinto mean materials comprising a lesser number of carbon atoms than foundin materials within the gasoline boiling range, preferably thosematerials containing 5 or less carbon atoms, that fit into any of thecategories of:

(a) Hydrogen-rich molecules, i.e. molecules with wt. % hydrogen rangingfrom about 13.0-25.0 wt. %. This may include light paraffins, i.e. CH₄,C₂ H₆, C₃ H₈ and other materials.

(b) i.e. a molecule whose chemical structure permits or favors thetransfer of carbon-hydrogen fragments. This includes CH₃ OH, other lowboiling alcohols such as ethanol, n-propanol, isopropanol, n-butanol,isobutanol, etc., aliphatic ethers, e.g., dimethyl ether, and otheroxygen compounds (acetals, aldehydes, ketones).

(c) Secondary Reaction Products from materials in categories (a) or (b)above that are carbon-hydrogen fragmentation compounds themselves, ortransfer hydrogen. This includes olefins, napthenes, or paraffins.

(d) Classes of materials which are structurally or chemically equivalentto those of category (c), noteably olefins, etc.; and

(e) A combination of any or all of the materials in categories (a)through (d). The preferred carbon-hydrogen fragmentation compounds aremethanol, dimethyl ether and C₂ -C₅ olefins, with methanol and dimethylether being the most preferred.

The terms "crude oil feed" is used herein to denominate any full rangecrude oil from primary, secondary or tertiary recovery from conventionalor offshore oil fields. "Crude oil feeds" may include any full range"syncrude" such as those that can be derived from coal, shale oil, tarsands and bitumens. The crude may be virgin (straight run) or generatedsynthetically by blending. It is generally desirable, however, to firstdesalt the crude since sodium, generally in the form of sodium chloride,is known to be a poison for most cracking operations. Surprisingly, ithas been found that LZ-210-A has an especially high tolerance for sodiumas compared with Zeolite Y or LZ-210. Further the term crude oil feed ismeant to include component parts of the crude which are generallyemployed as catalytic cracking feeds or potential feeds therefor andinclude feeds such as distillate gas oils, heavy vacuum gas oils,atmospheric and vacuum resids, syncrudes (from shale oil, tar sands,coal), pulverized coal and fractions boiling above the traditional endof the gasoline boiling range which generally includes compoundscontaining greater than about eleven carbon atoms and combinationsthereof.

Further, the FCC-CHFC process is believed to involve combinationreactions which are believed to be effective, at least in part, inremoving sulfur, oxygen, nitrogen and metal contaminants found in awhole crude or a heavy hydrocarbon portion thereof.

The operation of an FCC-CHFC type process is generally carried out attemperatures within the range of 400° F. up to about 1400° F. and moreusually within the range of 700° F. to about 1200° F. at pressuresselected from within the range of below atmospheric up to severalhundred pounds but normally less than 100 psig. Preferred conditionsinclude a temperature within the range of about 800° F. to about 1150°F. and pressures within the range of atmospheric to about 200 psig andhigher.

The carbon-hydrogen fragmentation compound may be provided to theprocess in most any way so long as it is present when contact with thecatalyst material is effected, i.e. in situ generation is suitable.

In the preferred operation an FCC-CHFC process methanol is used incombination with a gas oil type of hydrocarbon charge stock. The weightpercent of methanol in the hydrocarbon charge passed to the cracking orconversion operation will vary considerably and may be selected fromwithin the range of between about 1% and about 25 percent by weight, itbeing preferred to maintain the ratio within the range between about 5%and about 20, based on the weight of the feed. However, this may varydepending upon the hydrogen deficiency of the high molecular weighthydrocarbon charge, the amount of sulfur, nitrogen and oxygen in the oilcharge, the amount of polycyclic aromatics, the type of catalystemployed, and the level of conversion desired. It is preferred to avoidproviding any considerable or significant excess of methanol with thecharge because of its tendency to react with itself under someconditions.

The FCC-CHFC process preferably employs a fluidized catalyst system atlow pressures without the need for high pressure hydrogen gas. Such asystem promotes the highly efficient contact of relatively inexpensivecarbon-hydrogen fragmentation compounds with heavy, refractory moleculesin the presence of high-surface area cracking catalyst. Intermolecularhydrogen-transfer interactions, e.g., methylating reactions, andcatalytic cracking reactions are effected in the presence of fluidizedcatalyst particles and act to minimize problems due to diffusion/masstransport limitations and/or heat transfer.

The FCC-CHFC process can make use of the relatively cheapcarbon-hydrogen fragmentation compounds readily available in petroleumrefineries, such as light gas fractions, light olefins, low boilingliquid streams, etc., and, in particular, can employ methanol, a productwhich is readily available in quantity, either as a transportableproduct from overseas natural gas conversion processes, or as a productfrom large scale coal, shale, or tar sand gasification. It also canutilize carbon monoxide (in combination with contributiors such as wateror methanol), which gas is readily available from refinery regenerationflue gas (or other incomplete combustion processes), or from coal,shale, or tar sand gasification. Highly efficient recycle ofcarbon-hydrogen fragmentation compounds can also be effected.

The following examples were carried out to illustrate the instantinvention and are not intended to be limiting thereof. The experimentalprocedure employed was described in copending U.S. Ser. No. 315,853.

COMPARATIVE EXAMPLES 1 TO 4

The catalysts of examples 1 to 4 were prepared using commerciallyavailable Y-zeolites (referred to herein as Reference Zeolites A and B)having SiO₂ to Al₂ O₃ ratios of 5.1 (examples 1 and 2) and 4.9 (examples3 and 4), respectively. Zeolite B was twice ammonium exchanged prior tothe aluminum exchange so as to lower the Na₂ O content.

Examples 2 and 4 were carried out by slurrying 100 grams of ReferenceZeolites A or B, respectively, in 1 liter of 0.1M aluminum nitrate(Al(NO₃)₃.9H₂ O) for two hours at ambient temperature (18° C. to 24°C.). The product was filtered, washed with distilled water and dried inair at 100° C.

The results of the measurement of the physical and chemical propertiesof the zeolites are set forth in Table I. For comparison purposesexamples 1 and 3 (non-aluminum exchanged) should be compared withexamples 2 and 4 (aluminum exchanged), respectively.

With respect to Table I and all Tables set forth hereinafter in theexamples the footnotes 1, 2, 3 and 4 are employed to mean the following:

                  TABLE I                                                         ______________________________________                                                      Example                                                                       1      2       3        4                                       ______________________________________                                        Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                           5.1      5.1     4.9    4.9                                   Exchange Ion    None     Al.sup.+3                                                                             None   Al.sup.+3                             Chemical Analysis:                                                            % Exchanged Al.sub.2 O.sub.3.sup.(1)                                                          0        3.9     0      3.2                                   % Na.sub.2 O    2.25     2.07    1.09   1.03                                  % (NH.sub.4).sub.2 O                                                                          9.5      4.5     10.0   5.3                                   % Al.sub.2 O.sub.3 (Framework).sup.(2)                                                        22.0     21.9    22.5   22.7                                  % SiO.sub.2     65.4     65.2    65.4   65.9                                  Infrared Analysis:                                                            Assymetric Framework                                                                          --       1020    1018   1020                                  Stretch (cm..sup.-1)                                                          Symmetric Framework                                                                           --       786     784    785                                   Stretch (cm..sup.-1)                                                          Hydroxyl Intensity at 500° C.                                                          --       0.375   2.21   .357                                  Physical Analysis:                                                            XRD Peak Area.sup.(3)                                                                         100      83.7    100    79.2                                  Unit Cell Constant                                                                            24.73    24.69   24.73  24.82                                 O.sub.2 Capacity                                                                              34.1     29.4    35.3   29.4                                  Surface Area    876      745     918    718                                   DTA Collapse T, °C.                                                                    884      946     852    910                                   ______________________________________                                         .sup.(1) % Exchanged Alumina                                                  ##STR4##                                                                      .sup.(2) % Al.sub.2 O.sub.3 (framework) = % Al.sub.2 O.sub.3.sbsb.FINAL -     % Exchanged Alumina                                                           .sup.(3) Relative to unexchanged LZ210 or Y zeolite.                          .sup.(4) DTA = Differential Thermal Analysis.                            

COMPARATIVE EXAMPLES 5 TO 8

The zeolites prepared in examples 1 to 4 were evaluated in examples 5 to8, respectively for hydrothermal stability by measuring the percentcrystal retention after each zeolite was subjected to a hydrothermaltreatment.

The hydrothermal treatment was carried out in a horizontal tube furnacefitted with a Vycor furnace tube connected to a steam generator set toproduce 23%±2 steam in air at a flow-rate of 2.5 cubic feet per hour.The "hot zone" of the furnace was preheated in the gas flow to 873° C.±4before the zeolite samples were introduced to the furnace. The zeolitewas introduced into the furnace by placing about 2 grams of the hydratedsample into a shallow 3-inch long ceramic boat and then thrust into thehot zone of the furnace. In each case the sample boats were tiedtogether and each experiment contained a reference catalyst which was anammonium exchanged steam stabilized Y-zeolite. After a heating period offive (5) hours in 23%±2 steam the furnace was opened and the hotcatalysts removed. The catalysts were hydrated at room temperature in awater containing chamber for at least 48 hours. The catalysts wereanalyzed to determine their O₂ capacity, surface area and XRD peak areabefore and after the hydrothermal treatment. The results of thesemeasurements are both shown in Table II. The data show that both thestarting Y and ammonium-exchange Y are adversely affected, i.e.,degraded, by the hydrothermal treatment and retain an average of only2.9 and 4.1% crystallinity, respectively. The results also show thataluminum cation exchange does nothing to improve the hydrothermalstability of the Y zeolite. In fact, after aluminum exchange andhydrothermal stability of the Y zeolites decreased (based on thecrystallinity retention) to 0 and 1.7%, respectively.

EXAMPLES 9 TO 30

LZ-210 and LZ-210-A zeolites were prepared according to the procedure ofU.S. Ser. No. 315,853 using as the starting material a zeolite Y havinga SiO₂ to Al₂ O₃ ratio of about 5. The SiO₂ to Al₂ O₃ ratios of theresulting LZ-210 and LZ-210-A compositions are shown in Table III. Thezeolites of examples 11, 12, 16, 17 and 18 were ammonium exchanged tolower the Na₂ O content. The aluminum exchange was carried out as shownin the examples by a procedure similar to that employed in Examples 1 to4.

Table III shows that the thermal stability of LZ-210-A is general betterthan that observed for LZ-210 which has not been exchanged with analuminum cation. The improved thermal stability of LZ-210-A is readilyobservable from the DTA Collapse temperature which shows that LZ-210-Ahas a generally higher DTA Collapse temperature. Table III providescomparisons between LZ-210 and aluminum exchanged LZ-210 by comparingthe examples as follows: 9 with 10; 11 with 12, 13 with 14 and 15; 16with 17 and 18; 19 with 20 and 21; 22 with 23 and 24; 25 with 26 and 27;and 28 with 29 and 30.

                  TABLE II                                                        ______________________________________                                                       Example                                                                       5      6      7        8                                       ______________________________________                                        Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                            5.1      5.1    4.9    4.9                                   Exchange Ion     None     Al.sup.+3                                                                            None   Al.sup.+3                             % Al.sub.2 O.sub.3 Exchange.sup.(1)                                                            0        3.9    0      3.2                                   % Na.sub.2 O     2.25     2.07   1.09   1.03                                  Crystal Retention*                                                            % O.sub.2 Capacity Retention                                                                   7.6      0.0    4.9    2.9                                   % Surface Area Retention                                                                       1.0      0.0    3.3    2.1                                   % XRD Peak Area Retention                                                                      0.0      0.0    4.0    0.0                                   Average % Retention                                                                            2.9      0.0    4.1    1.7                                   ______________________________________                                         .sup.(1) % Exchanged Al.sub.2 O.sub.3                                         =-                                                                            ##STR5##                                                                      *After steaming at 870° C., 23° C. steam.                  

                                      TABLE III                                   __________________________________________________________________________    Example:     9   10 11  12 13  14 15 16  17 18 19                             __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                        6.5 6.5                                                                              6.5 6.5                                                                              7.4 7.4                                                                              7.4                                                                              8.4 8.4                                                                              8.4                                                                              8.4                            Exchange Ion None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None                           Chemical Analysis:                                                            % Exchanged Al.sub.2 O.sub.3.sup.(1)                                                        0  3.2                                                                               0  3.3                                                                                0 2.6                                                                              2.7                                                                                0 2.6                                                                              2.8                                                                                0                            % Na.sub.2 O 2.3 2.0                                                                              --   0.42                                                                             1.28                                                                             1.5                                                                              1.3                                                                               0.05                                                                              0.07                                                                             0.12                                                                             1.13                          % (NH.sub.4).sub.2 O                                                                       6.8 2.7                                                                              8.6 4.4                                                                              6.3 3.2                                                                              2.9                                                                              7.6 4.0                                                                              3.7                                                                              6.1                            % Al.sub.2 O.sub.3 (Framework).sup.(2)                                                     18.9                                                                              18.8                                                                             18.7                                                                              18.7                                                                             17.1                                                                              17.1                                                                             17.0                                                                             15.3                                                                              15.6                                                                             15.5                                                                             15.7                           % SiO.sub.2  71.9                                                                              71.4                                                                             71.0                                                                              71.0                                                                             74.9                                                                              74.7                                                                             74.5                                                                             75.3                                                                              76.7                                                                             76.4                                                                             77.3                           DTA Collapse T, °C.                                                                 973 1002                                                                             940 978                                                                              1016                                                                              1050                                                                             1046                                                                             1031                                                                              1061                                                                             1058                                                                             1058                           __________________________________________________________________________    Example:     20  21 22  23 24 25   26 27 28  29 30                            __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3 :                                                      8.4 8.4                                                                              9.0 9.0                                                                              9.0                                                                              9.1  9.1                                                                              9.1                                                                              11.0                                                                              11.0                                                                             11.0                          Exchange Ion:                                                                              Al.sup.+3                                                                         Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None Al.sup.+3                                                                        Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                     Chemical Analysis:                                                            % Exchanged Al.sub.2 O.sub.3.sup.(1)                                                       2.7 3.0                                                                                0 2.3                                                                              2.2                                                                                0  3.7                                                                              3.0                                                                                0 3.3                                                                              3.3                           % Na.sub.2 O  0.95                                                                              0.79                                                                             1.28                                                                              0.93                                                                             1.01                                                                            1.2   0.85                                                                             0.83                                                                             0.39                                                                              0.44                                                                             0.45                         % (NH.sub.4).sub.2 O                                                                       3.0 2.6                                                                              6.1 2.5                                                                              2.7                                                                              6.2  2.9                                                                              3.2                                                                              5.1 2.2                                                                              1.6                           % Al.sub.2 O.sub.3 (Framework).sup.(2)                                                     15.7                                                                              15.7                                                                             14.5                                                                              15.0                                                                             15.0                                                                             14.3 14.2                                                                             14.5                                                                             12.3                                                                              12.3                                                                             12.7                          % SiO.sub.2  77.5                                                                              77.5                                                                             77.0                                                                              79.5                                                                             79.2                                                                             76.4 76.0                                                                             77.3                                                                             79.5                                                                              79.2                                                                             82.2                          DTA.sup.(4) Collapse T, °C.                                                         --  1067                                                                             1061                                                                              1067                                                                             1067                                                                             1064 1082                                                                             1067                                                                             1110                                                                              1108                                                                             --                            __________________________________________________________________________

EXAMPLES 31 TO 52

The zeolites set forth in examples 9 to 30 were evaluated, respectively,in examples 31 to 52 for their hydrothermal stability by the procedureemployed for examples 5 to 8. The results are shown in Table IV. Thedata show that aluminum exchange of LZ-210 increases the hydrothermalstability of the LZ-210 composition. This is opposite the resultobserved for zeolite Y as shown in Examples 5 to 8. There were only twocases (example 38 having a low Na₂ O content (0.05%) and example 31having a low SiO₂ /Al₂ O₃ ratio (6.5) with high Na₂ O content (2.3%))where the hydrothermal stability was not improved by aluminum exchanged.Although the reason for these two results are not understood it isbelieved that by proper correlation of the SiO₂ /Al₂ O₃ ratio and theNa₂ O content that improvement in the hydrothermal stability may beobserved.

The data in Table IV provide comparisons between LZ-210 and LZ-210-A(aluminum exchanged LZ-210) by comparing the examples as follows: 31with 32; 33 with 34, 35 with 36 and 37; 38 and 39 and 40; 41 with 42 and43; 44 and 45 and 46; 47 and 48 and 49; 50 and 51 and 52.

                                      TABLE IV                                    __________________________________________________________________________    Example:     31  32 33  34 35  36 37 38  39 40 41                             __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                        6.5 6.5                                                                               6.5                                                                              6.5                                                                              7.4  7.4                                                                              7.4                                                                              8.4                                                                              8.4                                                                              8.4                                                                              8.4                            Exchange Ion None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None                           Chemical Analysis:                                                            % Exchanged Al.sub.2 O.sub.3.sup.(1)                                                       0   3.2                                                                              0   3.3                                                                              0    2.6                                                                              2.7                                                                              0  2.6                                                                              2.8                                                                              0                              % Na.sub.2 O 2.3 2.0                                                                               0.38                                                                             0.42                                                                              1.28                                                                              1.5                                                                              1.3                                                                             0.05                                                                              0.07                                                                             0.12                                                                              1.13                          Crystal Retention*                                                            % O.sub.2 Capacity Retention                                                               2.7 1.7                                                                              55.8                                                                              58.0                                                                             5.8 50.1                                                                             40.9                                                                             72.5                                                                              76.6                                                                             74.6                                                                             47.9                           % Surface Area Retention                                                                   0.5 0.4                                                                              55.4                                                                              75.6                                                                             3.7 -- 40.2                                                                             71.8                                                                              76.1                                                                             74.7                                                                             46.6                           % XRD Peak Retention                                                                       0.0 0.0                                                                              42.5                                                                              62.6                                                                             0.0 59.6                                                                             38.8                                                                             85.0                                                                              85.6                                                                             85.3                                                                             57.9                           Average % Retention                                                                        1.1 0.7                                                                              50.9                                                                              65.4                                                                             3.2 54.9                                                                             40.0                                                                             76.7                                                                              79.4                                                                             78.2                                                                             50.8                           __________________________________________________________________________    Example:     42  43 44  45 46 47  48  59 50  51 52                            __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                        8.4 8.4                                                                               9.0                                                                              9.0                                                                              9.0                                                                               9.1                                                                              9.1 9.1                                                                              11.0                                                                              11.0                                                                             11.0                          Exchange Ion Al.sup.+3                                                                         Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                         Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                        Al.sup.+3                     Chemical Analysis:                                                            % Exchanged Al.sub.2 O.sub.3.sup.(1)                                                       2.7 3.0                                                                              0   2.3                                                                              2.2                                                                              0   3.7 3.0                                                                              0   3.3                                                                              3.3                           % Na.sub.2 O  0.95                                                                              0.79                                                                              1.28                                                                             0.93                                                                             1.01                                                                             1.2                                                                               0.85                                                                              0.83                                                                             0.39                                                                              0.44                                                                             0.45                         Crystal Retention*                                                            % O.sub.2 Capacity Retention                                                               72.1                                                                              60.0                                                                             20.5                                                                              62.4                                                                             50.5                                                                             33.6                                                                              68.4                                                                              57.0                                                                             70.3                                                                              74.8                                                                             77.4                          % Surface Area Retention                                                                   80.3                                                                              62.0                                                                             33.3                                                                              54.0                                                                             54.4                                                                             31.0                                                                              64.7                                                                              -- 71.5                                                                              69.5                                                                             --                            % XRD Peak Retention                                                                       --  92.0                                                                             41.2                                                                              74.2                                                                             76.8                                                                             41.8                                                                              79.8                                                                              72.3                                                                             70.0                                                                              90.0                                                                             --                            Average % Retention                                                                        76.2                                                                              71.3                                                                             34.3                                                                              63.5                                                                             60.6                                                                             35.5                                                                              71.0                                                                              64.6                                                                             70.6                                                                              78.1                                                                             77.4                          __________________________________________________________________________     *After destructive steaming at 870° C., 23° C. steam.      

EXAMPLES 53 TO 76

The effect of aluminum exchange on the hydrothermal stability of LZ-210as compared with rare earth cation exchange was determined by rare-earthexchanging several LZ-210 compositions. The patent literature hasreported that Y zeolites do show a slight improvement in hydrothermalstability upon rare earth ion exchange. The LZ-210 compositions ofexamples 54, 56, 58, 60 and 63 were rare earth exchanged to form thecompositions of 55, 57, 59, 61, 62 and (64 and 65), respectively, usinga mixture (solution) of rare earth chlorides (Molycorp's Product No.5240) having a rare earth analysis of:

    ______________________________________                                                  Wt. %                                                               ______________________________________                                                Ce  2.8                                                                       La  14.7                                                                      Nd  4.5                                                                       Pr  3.3                                                               ______________________________________                                    

The rare earth exchange was carried out using a 1 hour reflux. Theresults are shown in Table V. The data show that rare-earth exchangegave an increase in the DTA collapse temperature indicating an increasein the thermal stability.

The hydrothermal stability of these catalysts were evaluated by theprocedure employed in Examples 5 to 8. The results are reported in TableVI. The data show that no significant improvement in hydrothermalstability was observed by the rare earth exchange whereas aluminumexchange did provide a significant improvement in hydrothermalstability.

                                      TABLE V                                     __________________________________________________________________________    Example:  53  54  55  56  57  58  59  60  61  62  63  64                      __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                     7.5  7.5                                                                              7.9 7.9 8.3 8.3 9.1 9.1 9.1 11.0                                                                              11.0                                                                              11.0                    Exchange Ion                                                                            None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  RE.sub.2 O.sub.3        Chemical Analysis:                                                            % RE.sub.2 O                                                                              0  5.77                                                                              0  6.19                                                                               0  5.58                                                                               0  6.15                                                                              2.27                                                                                0  5.8                                                                               5.7                    % Na.sub.2 O                                                                             1.28                                                                              1.19                                                                              0.26                                                                             0.27                                                                               1.13                                                                             0.95                                                                              1.2 1.07                                                                              1.22                                                                               0.39                                                                              0.31                                                                              0.40                   % (NH.sub.4).sub.2 O                                                                    6.3  3.8                                                                               7.23                                                                             4.92                                                                              6.1 3.64                                                                              6.2 3.75                                                                              5.26                                                                               5.1                                                                               2.6                                                                               2.6                    % Al.sub.2 O.sub.3                                                                      17.1                                                                              16.5                                                                              16.58                                                                             16.04                                                                             15.7                                                                              15.3                                                                              14.3                                                                              14.7                                                                              15.4                                                                              12.3                                                                              11.7                                                                              12.5                    % SiO.sub.2                                                                             74.9                                                                              72.5                                                                              76.65                                                                             71.97                                                                             77.3                                                                              74.8                                                                              76.4                                                                              76.7                                                                              79.5                                                                              79.5                                                                              78.8                                                                              78.7                    Cation/Aluminum                                                                          .85                                                                                .90                                                                              .88                                                                               .99                                                                               .88                                                                               .91                                                                               .99                                                                              1.01                                                                               .94                                                                                .87                                                                               .94                                                                               .89                   % RE Exchange                                                                           --  32.6                                                                              --  36.0                                                                              --  34.0                                                                              --  39.0                                                                              13.8                                                                              --  46.2                                                                              42.5                    Physical Analysis:                                                            XRD Peak Area*                                                                           100                                                                              66.2                                                                              100 56.4                                                                              100 63.1                                                                              100 67.9                                                                              87.3                                                                              100 65.8                                                                              63.6                    Unit Cell Constant                                                                      24.56                                                                              24.60                                                                            24.6                                                                              24.57                                                                             24.53                                                                             24.55                                                                             24.51                                                                             24.56                                                                             24.53                                                                              24.46                                                                             24.52                                                                             24.48                  O.sub.2 Capacity                                                                        31.2                                                                              33.2                                                                              34.7                                                                              31.2                                                                              31.5                                                                              29.8                                                                              33.7                                                                              32.4                                                                              31.6                                                                              31.0                                                                              30.5                                                                              30.1                    Surface Area                                                                             890                                                                               731                                                                              927  866                                                                              814 596 855  861                                                                               831                                                                               840                                                                               830                                                                              705                     DTA Collapse T, °C.                                                              1016                                                                              1083                                                                              998 1079                                                                              1058                                                                              --  1064                                                                              1099                                                                              1097                                                                              1110                                                                              1131                                                                              --                      __________________________________________________________________________     *Relative to unexchanged LZ210, expressed as a percentage.               

                                      TABLE VI                                    __________________________________________________________________________    Example:       65  66  67  68  69  70  71  72  73  74  75  76                 __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                          7.5 7.5  7.9                                                                               7.9                                                                               8.3                                                                               8.3                                                                               9.1                                                                              9.1  9.1                                                                              11.0                                                                              11.0                                                                              11.0               Exchange Ion   None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  RE.sub.2 O.sub.3                                                                  None                                                                              RE.sub.2 O.sub.3                                                                  RE.sub.2                                                                      O.sub.3            % RE Exchanged --  32.6                                                                              --  36.0                                                                              --  34.0                                                                              --  39.0                                                                              13.8                                                                              --  46.2                                                                              42.5               % Na.sub.2 O    1.28                                                                              1.19                                                                              0.26                                                                              0.27                                                                              1.13                                                                              0.95                                                                              1.2                                                                               1.07                                                                              1.22                                                                              0.39                                                                              0.31                                                                              0.40              Crystal Retention*:                                                           % O.sub.2 Capacity Retention                                                                 5.8 4.5 66.8                                                                              60.1                                                                              47.9                                                                              42.6                                                                              33.6                                                                              4.3 14.3                                                                              70.3                                                                              60.9                                                                              58.6               % Surface Area Retention                                                                     3.7 5.8 --  60.9                                                                              46.6                                                                              58.9                                                                              31.0                                                                              6.6 13.6                                                                              71.5                                                                              61.3                                                                              72.6               % XRD Peak Area Retention                                                                    0.0 22.8                                                                              61.3                                                                              77.4                                                                              57.9                                                                              --  41.8                                                                              47.0                                                                              24.9                                                                              70.0                                                                              79.8                                                                              --                 Average % Retention                                                                          3.2 10.9                                                                              64.1                                                                              66.1                                                                              50.8                                                                              50.7                                                                              35.5                                                                              19.3                                                                              17.6                                                                              70.6                                                                              67.3                                                                              65.6               __________________________________________________________________________     *After destructive steaming at 870° C., 23% Steam.                

EXAMPLES 77 TO 90

Examples 77 to 90 are examples employing LZ-210 and LZ-210-Acompositions as cracking catalysts. In each case LZ-210 and the LZ-210-Aderived therefrom were evaluated as cracking catalysts. The LZ-210 orLZ-210-A was formulated into a cracking catalyst by mixing 15% zeolite(LZ-210 or LZ-210-A) with 85% alumina (anhydrous basis), based on thetotal catalyst weight. The catalysts were prepared by mixing the zeolitewith alumina (65% based on the final total) in a Hobart mixer. Then aboehmite alumina (20%, based on the final total) was added and thecomposite extruded into 1/16" extrudates. The extrudates were dried at100° C. The dried extrudates were then calcined in dry air at 500° C.and then treated at 840° C. in 23% steam for 17 hours. The lattertreatment comprised heating the extrudates to 750° C. in static air from500° C. at the rate of 12 to 16° C. per minute followed by introductionof the air/steam mixture and heating to 840° C. and heating at 840° C.for 17 hours.

The catalysts were sized to 60/100 mesh (U.S. Standard) and thenevaluated by ASTM D-3907 for use as cracking catalysts. The results areshown in Table VII. The data show that the aluminum exchange not onlyenhances hydrothermal stability but also may in some instance improveactivity and selectivity to the gasoline fraction.

                                      TABLE VII                                   __________________________________________________________________________              Example                                                                       77  78 79  80  81  82 83  84  85  86  87  88  89  90                __________________________________________________________________________    Initial SiO.sub.2 /Al.sub.2 O.sub.3                                                     6.5 6.5                                                                              7.4 7.4 8.3 8.3                                                                              9.0 9.0 9.1 9.1 11.0                                                                              11.0                                                                              11.0                                                                              11.0              Exchange Ion                                                                            None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                         None                                                                              Al.sup.+3                                                                        None                                                                              Al.sup.+3                                                                         None                                                                              Al.sup.+3                                                                         None                                                                              Al.sup.+3                                                                         None                                                                              Al.sup.+3         MAT Conversion.sup.(1)                                                                  51.0                                                                              39.0                                                                             72.5                                                                              73.6                                                                              72.4                                                                              71.6                                                                             70.2                                                                              65.3                                                                              66.3                                                                              69.3                                                                              71.3                                                                              73.7                                                                              66.9                                                                              68.4              MAT Selectivity at                                                                      .sup.(3)                                                                          .sup.(3)                                                        70% Conversion.sup.(2)                                                        % Gasoline                                                                              .sup.(3)                                                                          .sup.(3)                                                                         50.0                                                                              51.6                                                                              50.4                                                                              50.2                                                                             54.5                                                                              54.2                                                                              52.5                                                                              53.4                                                                              49.2                                                                              52.4                                                                              54.8                                                                              53.9              % Gas     .sup.(3)                                                                          .sup.(3)                                                                         15.9                                                                              13.9                                                                              15.0                                                                              13.9                                                                             11.6                                                                              11.6                                                                              13.0                                                                              12.6                                                                              16.6                                                                              13.8                                                                              10.8                                                                              11.8              % Coke    .sup.(3)                                                                          .sup.(3)                                                                         4.4 4.8 4.9 6.3                                                                              4.2 4.6 5.0 4.3 4.2 4.0 4.8 4.5               __________________________________________________________________________     .sup.(1) Average of triplicate MAT runs. (ASTM D3907).                        ##STR6##                                                                      .sup.(3) Conversion too low to predict selectivity.                      

We claim:
 1. The zeolitic aluminosilicate having a mole ratio of oxidein the dehydrated state of:

    0.85-1.1 M.sub.2/n O:Al.sub.2 O.sub.3 :XSiO.sub.2

wherein M is a cation having valence "n"; "X" has a value greater than6.0, has an X-ray powder diffraction pattern having at least thed-spacings of Table A; has extraneous silicon atoms in he crystallattice in the form of framework SiO₄ tetrahedra; and has at least oneGroup IIIA cation per unit cell.
 2. The zeolitic aluminosilicate ofclaim 1 having at least two Group III cations per unit cell.
 3. Thezeolitic aluminosilicate of claim 2 having at least three Group IIIAcations per unit cell.
 4. The zeolitic aluminosilicate of claim 1wherein the Group IIIA cation is aluminum.
 5. The zeoliticaluminosilicate of claim 1 wherein "x" has a value greater than 7.0. 6.A catalyst for cracking hydrocarbons comprising between about 1 percentand about 99 percent by weight of an inorganic matrix and about 1percent and about 99 percent by weight of the zeolitic aluminosilicateof claim
 1. 7. The zeolitic aluminosilicate according to claim 1 whereinthe aluminosilicate contains an effective amount of at least onemultivalent cation selected from the group consisting of cerium,lanthanum, praseodymium, neodymium, promethium, samarium, europium,galodinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,lutetium and mixtures thereof.
 8. The zeolitic aluminosilicate of claim1 wherein the zeolitic aluminosilicate is defined as having a chemicalcomposition expressed in terms of mole fractions of framework tetrahedraas:

    [Al.sub.(a-N) Si.sub.b+(N-Δz) □.sub.z ]O.sub.2

wherein: "□" denotes the defect sites; "z" is the mole fraction ofdefect sites in the zeolite framework; "N" is the mole fraction ofaluminum tetrahedra removed from the framework; "a" is the mole fractionof aluminum tetrahedra present in the framework of the starting zeolite;"b" is the mole fraction of the silicon tetrahedra present in theframewok of the starting zeolite; "(N-Δz)" is the mole fraction incresein silicon tetrahedra; "Δz" is the net change in the mole fraction ofdefect sites; ##EQU6## has a value greater than 3; the change in defectstructure factor Δz is less than 0.08; an increased silicon content inthe framework, ##EQU7## of at least 0.5; and a cation equivalentexpressed as a monovalent cation species, M⁺ /Al, from 0.85 to 1.1 andthe characteristic crystal structure of zeolite Y is indicated by anX-ray powder diffraction pattern having at least the d-spacings setforth broadly in Table A.
 9. The zeolitic aluminosilicate of claim 8wherein the change in defect structure Δz is less than 0.05.
 10. Thezeolitic aluminosilicate of claim 8 wherein the cation equivalentexpresses a multivalent cation species, M^(+n) /Al, where n is 2 or 3.11. The zeolitic aluminosilicate of claim 1 wherein the value of "x" is7.0.
 12. The process for the preparation of a cracking catalystcomprising the treatment of a zeolitic aluminosilicate which has a moleratio of oxides in the dehydrated state of

    (0.85-1.1)M.sub.2/n O:Al.sub.2 O.sub.3 : X SiO.sub.2

wherein M is a cation having a valence of "n"; "X" has a value greaterthan 6.0 has an x-ray powder diffraction pattern having at least thed-spacings of Table A; has extraneous silicon atoms in the crystallattice in the form of framework SiO₄ tetrahedra; and has beenion-exchanged with an effective amount of at least one Group IIIAcation.
 13. The cracking catalyst prepared by the process of claim 12.14. The process according to claim 12 wherein the aluminosilicate ision-exchanged with a multivalent cation selected from the groupconsisting of cerium, lanthanum, praseodymium, neodymium, promethium,samarium, europium, galodinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, lutetium and mixtures thereof.
 15. The process ofclaim 12 wherein the zeolitic aluminosilicate is defined as having achemical composition expressed in terms of mole fractions of frameworktetrahedra as:

    [Al.sub.(a-N) Si.sub.b+(N-Δz) □z]O.sub.2

wherein: "□" denotes the defect sites; "z" is the mole fraction ofdefect sites in the zeolite framework; "N" is the mole fraction ofaluminum tetrahedra removed from the framework; "a" is the mole fractionof aluminum tetrahedra present in the framework of the starting zeolite;"b" is the mole fraction of the silicon tetrahedra present in theframework of the starting zeolite; "(N-Δz)" is the mole fractionincrease in silicon tetrahedra; "Δz" is the net change in the molefraction of defect sites; ##EQU8## has a value greater than 3; thechange in defect structure factor Δz is less than 0.08; an increasedsilicon content in the framework, ##EQU9## of at least 0.5; and a cationequivalent expressed as a monovalent cation species, M⁺ /Al, from 0.85to 1.1 and the characteristic crystal structure of zeolite Y isindicated by an X-ray powder diffraction pattern having at least thed-spacings set forth broadly in Table A.
 16. The process of claim 15wherein the change in defect structure Δz is less than 0.05.
 17. Thezeolitic aluminosilicate of claim 8 wherein the cation equivalentexpresses a multivalent cation species, M^(+n) /Al, where n is 2 or 3.18. The process of claim 12 wherein the value of "x" is greater than 7.19. A catalyst for catalytic cracking a hydrocarbon feedstock whereinsaid catalyst comprises an effective amount of the zeoliticaluminosilicate of claim 12 and between about 1 and about 99 percent byweight of an inorganic oxide matrix.
 20. The catalyst of claim 19wherein the inorganic oxide matrix is at least one selected from thegroup consisting of clays, silicas, aluminas, silica-aluminas,silica-zirconias, silica-magnesias, alumina-borias, alumina-titanias andthe like.